1. Field of the Invention
The present invention pertains to fire retardant polystyrene compositions. More particularly, it pertains to a method for reducing the dripping tendency of fire retardant polystyrene compositions under flaming conditions.
2. Description of the Prior Art
Polystyrene compositions are well known in the prior art. Many attempts have been made to impart some degree of flame retardancy to these materials in order to make them slower to ignite and slower to burn.
A number of additives have been found, i.e., sulfur, sulfur compounds, phosphorous compounds, halogen compounds, etc., that are effective in increasing the resistance of polystyrene compositions to ignition and in slowing down the rate of burning of these materials. Many otherwise suitable fire retardant additives failed to achieve acceptance or commercial success because they caused the polystyrene compositions to drip in a fire situation. This is undesirable and results in a lower UL-94 rating, since dripping, despite short flame-out times, will reduce the flame spread rating from an expected V-0 to an undesirable V-2.
Dripping is also found in some fire retardant compositions, not because of the additives, but because of the molecular weight of the polymer component. Usually, this is the case where, by choice or necessity, a low molecular weight polymer is used.
Regardless of the cause, a need exists in the art for a method for reducing the dripping tendency of polystyrene compositions under flaming conditions.